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Rangefinder Laser dissection

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LAN_403

Dr. Shark

Sat Apr 08 2006, 12:14PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

I recently got a rangefinder Laser from a russian tank from a guy from eBay. From the outside it looked fine, but before firing it up I thought I better take it apart and give it a good check-up.
This is what the parts look like, lined up nicely on a yellow background, very TDU-style

I have no idea how the optics are to be calibrated, everything just screws in place and there are no adjustments possible.

And this is the laser rod, in a most pittyful condition:

(out of focus, sorry, gotta get used to that new Nikon D50)
It looks like there was some kind of coating on the rod originally, but it has mostly just flaked of. I have no idea what it was, maybe some chemical that absorbs UV and flouresces at near 800nm. The ends of the rod are both heavily pitted, so either this laser has seen some heavy abuse (maybe the tank it came from got hit by a nuke?), or the russians just dont make quality lasers

Money not so well spend I think, it was cheap, but the only thing I can use out of it is the flashlamp. Well, bad luck I guess.

Self Defenestrate

Sat Apr 08 2006, 05:46PM

Registered Member #87 Joined: Thu Feb 09 2006, 01:36PM
Location: San Jose
Posts: 191

What are the dimensions on the rod? mi-lasers.com has some small rods, and ebay always has a flood of them as well.

Dr. Shark

Sat Apr 08 2006, 07:01PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

I've had more YAG rods in the past than you would probably belief. The problem is that just a rod and a flashlamp gets you pretty much nowhere, most of the sweat and money is in all the optics, mirror mounts and tuning. Since this rangefinder has no adjustment possibilites, and I'm not sure I would want to use that rotary q-switch that is in there, I doubt it would ever be lasing again, even with a suitable rod.

Sulaiman

Sun Apr 09 2006, 08:09AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Assuming the mirrors are ok, you could have a go at polishing the ruby rod ends
a lathe would help, a power drill may work?

Madgyver

Sun Apr 09 2006, 09:54AM

Registered Member #177 Joined: Wed Feb 15 2006, 02:16PM
Location: Munich, Germany
Posts: 214

Wouldn't one need a special paste or polishing agent to get it realy smooth? What could one use?

Hazmatt_(The Underdog)

Sun Apr 09 2006, 06:42PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

well...I think polishing will probably require having the rod hydrogen fire polished rather then grinding. Even with a very fine polish there will be small scratches in the surface. But a careful fire polishing would insure no scratches at all.
I could be wrong, that's just my impression.

Sulaiman

Sun Apr 09 2006, 09:00PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

THIS IS A QUESTION, NOT A SUGGESTION.

Since the Ruby Rod is monocrystaline

can it be cleaved?

(sheared along a crystaline plane)

Dr. Shark

Mon Apr 10 2006, 11:48AM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

nice to see some discussion here!

Firstly, let me clarify, this is a YAG rod, not ruby. They have similar properties though. I am nor sure along which crystal axis the rods are grown, but I have had broken rods in the past (told you I've had a few rods), and they break just like glass, not along a face.

Heating the crystal would not be a good idea I suspect, since this surely would modify the crystal structure and do weird things to the optical properties. It's not glass after all.

I might give polishing it a try, but from what I have heard from other people it is not worth the effort. Firstly, without the AR coating, there are properly going to be enough reflections to get the rod lasing without any external mirrors. With external mirrors in place this is bad news, since different cavity modes will be competing cause erratic operation.
Also I would not be able to grind the faces flat and parallel, I would have to make them slightly convex, which is good if I don't use external mirrors, but again very bad if I do.
I'll see, maybe I can somehow polish and mirror the ends and make a minimal parts count, non-tunable ghetto-laser? I'll have a grind at the rod and see how it machines

Sulaiman

Mon Apr 10 2006, 04:54PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Toothpaste makes quite a good/convenient grinding/lapping paste

Dr. Shark

Tue Apr 11 2006, 11:06AM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

I could give that a try. Actually, if I go through the trouble of setting up a laser cavity, I might aswell just try the rod as it is first. I dont know what to expect to happen, but most things I could do to the rod would probably just make it worse. With enough pump energy, it should be possible to get anything to lase

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